1. Field of the Invention
The present invention relates to lumbar supports for seats, and more particularly to seats having a belt-type lumbar support.
2. Related Art
Many different types of strap lumbar supports have been used in seating systems. Strap or belt-type lumbar supports can be any type of strap, including a belt or wire, and are known to be supported in the seat frame by various means, including springs, hooks, brackets, clips, and wires. Strap lumbar supports are also known to be operated using a number of different actuation devices. An example of a prior art belt lumbar support is shown in FIGS. 1A and 1B of the accompanying drawings. Other examples of prior art strap lumbar devices can be found in the following references: U.S. Pat. No. 3,258,259, U.S. Pat. No. 3,273,877, U.S. Pat. No. 4,155,592, U.S. Pat. No. 4,309,058, U.S. Pat. No. 4,462,635, U.S. Pat. No. 5,224,757, U.S. Pat. No. 5,482,353, U.S. Pat. No. 5,507,559, U.S. Pat. No. 5,685,606, U.S. Pat. No. 5,716,098, U.S. Pat. No. 5,769,490, U.S. Pat. No. 5,788,328, U.S. Pat. No. 5,797,652, U.S. Pat. No. 5,860,700, U.S. Pat. No. 6,152,531, U.S. Pat. No. 6,254,186, U.S. Pat. No. 6,394,546, U.S. Pat. No. 6,412,868, U.S. Pat. No. 6,471,294, U.S. Pat. No. 6,644,740, U.S. Pat. No. 6,918,634, US 2005/0023873, US 2004/0212227, EP 0296938, EP 0420824, EP 0540481, EP 0518830, EP 0582821, GB526572, FR 2596334, and FR 2765531.
Strap lumbar devices can usually be distinguished from arching lumbar devices, such as described and illustrated in U.S. Pat. No. 6,003,941 and U.S. Pat. No. 5,518,294, based on the difference between their respective tensioning elements. The strap lumbar is connected to the seat frame in a manner that the tensioning element must be pulled taut to increase support, and the tensioning element can be the strap itself, as with the belts in U.S. Pat. No. 4,155,592, or another structure, as with the Bowden cable in EP 0296938, or a combination thereof as with support and cables in U.S. Pat. No. 6,152,531. In comparison, the tensioning element in the arching lumbar is stiff and can be rotated, pushed or bowed to increase support. As particularly illustrated in FIGS. 1A and 1B, even in the case where the strap lumbar includes a rather stiff belt 2, the belt 2 is connected to a seat frame 6 through a traction cable 4. Increasing tension in the traction cable 4 pulls the belt 2 taut but does not arch the belt 2. As discussed below with reference to the present invention, the preferred traction cable 4 is a Bowden cable 50 which has a sheath 52 surrounding an inner wire core 54 that can slide within the sheath 52.
In belt lumbar devices, there are a number of different designs for the support elements and their cooperative relationship with the tensioning elements. Many strap lumbar supports are more flexible than the belt lumbar supports. Some supports form a part of the tensioning element and are themselves pulled taut between the seat frame, whereas other supports are merely pressed forward into the seat as the tensioning element is pulled taut.
Modular seat assembly techniques require components to be designed for ease and speed of assembly. Accordingly, along with the need for strong, economical, compact components in seat design, there is a continuing need in seat assembly procedures to increase the economy, speed and efficiency of component assembly and shipping. Furthermore, as described in US Pub. No. 2004/0108760 and U.S. Pat. No. 5,553,919, there is a benefit for providing spinal relief when supporting the spine or for using a shaped pad to provide comfort. It is preferable to apply lumbar supporting pressure bilaterally adjacent to the spinal column, while maintaining a vertical recess or channel to accommodate the vertebrae, because the bony vertebrae of the spine may become uncomfortable if direct pressure is applied to them by a lumbar support pressure surface.